Blast furnace treatment of low



Reisaued Apr. 7, 1942 BLAST FURNACE TREATMENT OF LOW GRADEMANGANESE-IRON ORE Percy H. Boyster, Montclair, N. J.

No Drawing. Original No. 2,265,863, dated December 9, 1941, Serial No.234,847, October 13,

1938. Serial No. 425,579

7 Claims.

This invention relates to the pyrometallurgy of oxidic ores containingsubstantial amounts both of iron and of manganese, as opposed toordinary iron ore containing only a few percent (e. g., 3% or less) ofmanganese compounds, and is concerned with the provision of an improvedmethod of smelting oxidic manganese-iron ore in the blast furnace forthe production of a metal and of an artificial manganese ore low iniron.

In my copending application for U. S. Letters Patent Serial No. 234,848filed October 13, 1938,

there is described a process of working up ores of the abovedescription, said process consisting essentially in a blast furnacetreatment of the ore with solid fuel, the process being characterized bythe employment of (1) a fuel-to-ore ratio materially lower than isconventional in blast furnace practice, and (2) a highly preheated blast(e. g., an air blast at above 1800 F.), the total heat supplied to thecharge (from combustion of ganese of the starting material.

Satisfactory operation of that process under blast furnace conditionscan be realized economically with high blast temperatures provided theore-to-fuel ratio is increased in the charge until the hearthtemperature is reduced to the unusually low range 2000 F. to 23'l0 F.Even at 2420 F. I have found in actual practice that I can produce metalwith as low as 1.75% Mn, 1. e., a metallization of 5.3% of the manganesein the charge and a retention in the slag of about 94.7% of the chargedmanganese.

By the expression hearth temperature" I mean the algebraic average ofthe temperatures observed withan optical pyrometer (corrected foremissivity) sighted on the emergent streams of metal and slag at cast"and flush, respectively. 1

The inventive object of the above described process is the provision ofthermal and chemical conditions in a blast furnace hearth favoring theselective reduction of iron oxide.

Thepresent invention has the same practical Application for reissueJanuary 3, 1942,

objectives as has the invention of the aforesaid copending patentapplication. This, it is an object of the present invention to provideconditions of blast furnace operation which shall effect the selectivereduction of iron from an oxidic manganese-iron ore so as to produce ametal and a slag of such relative contents of mo and FeO as to amount toan artificial mananese ore."

According to the improved process of the present invention, however, Itreat oxidic mange nese-iron ore in a blast furnace under nonequilibriumor "upset conditions of operation by impairing the intensity ofreduction in the hearth and by so altering the chemical, physical andmetallurgical conditions of usual practice that the effectiveness of theblast furnace hearth, ordinarily such a strongly reducing agent, isdepreciated. The present process may be characterized as a blast furnaceoperation purposefully carried out under conditions inimlcal to theattainment of thermodynamic equilibrium. That is to say, I so limit thetime, the degree of chemical contact, and the distribution of heat andof materials, that the free energy of reduction in the furnace hearth isdiminished, to the end that the FeO content of the slag emerging fromthe furnace is higher than would result from attainment of thermodynamicequilibrium.

In effecting notable departure from equilibrium conditions I may employone, or another, or a combination of two or more, of the followingmeasures: 1

1. Overburdening the furnace by the maintenance of too high an ore tofuel ratio;

2. Non-uniformly distributing the charge on the stock line;

3. Maintaining too short a stock column;

4.. Using poor coke;

5. Maintaining the slag level-in the hearth higher than customary;

6. Causing the oxidizing zone or zone of coke combustion to cover alarger fraction of the furnace hearth area than is customary;

7. Operating with a charge which'yields a slag low in C30 and MgO buthigh in iron and/or manganese;

8. Increasing the moisture content of the blast above normal.

A fuller explanation of these measures follows: 1. Overburdening is mostfrequently and readily indicated by'the appearance of a "scouringslag-i. e., a black slagrelatively high in FeO- and by theconcurrentproductio'n of pig iron of poor analysis, low in silicon andhigh in sulphur.

In conventional blast furnac practice overburdening and the consequentoccurrence of scouring slag is avoided but may inadvertently occur. Inthe present process, however, I may purposefully overburden in order toproduce a slag intentionally high in FeO, in order to maintain thedesired departure from equilibrium conditions.

2. Non-uniform distribution of ore and fuel on the stock line causes thecharge to descend in an irregular manner, permits the ascending gasstream to channel, and results in the injection into the bosh, tuyrezone and hearth of incompletely treated ore. thereby adversely affectingthe reduction efficiency of the hearth. In conventional blast furnacepractice non-uniform distribution of ore and fuel on the stock line isavoided: in the present process, however, I may purposefully anddesirably impair the reduction efficiency of the hearth in this manner.

3. Allowing the level of the charge to descend too low in the furnaceshaft reduces the length of the path of travel of the ore and fuel and.concurrently, the period of time within which the charge remains inchemical and thermal contact with the hot reducing gas ascending throughthe furnace. Thereby, the furnace is prevented in part from exercisingits normal metallurgical effect as a strong reducing means, a

and "raw ore (i, e., incompletely reduced iron oxide) arrives in theslag bath, upsetting the furnace operation as indicated by theappearance of one, two or three percent of FeO in the slag. While thiswould not, of course, be economically desirable in conventional blastfurnace practice, I may purposefully effect this measure in order tocontrol hearth conditions.

4. Charging coke of poor combustibilitydue to (a) low porosity, (b)improper coking, (0) high ash content, (d) defective cell structure or(e) abnormal graphitization of carbon-likewise has an adverse effect onreduction. With reduced coke combustibility, the fraction of the furnacehearth area in which the oxidizing gases ()2, CO2 and H20 exist isincreased and the FeO content of the slag is elevated above itsequilibrium value and above that value sought in conventional blastfurnace practice.

5. The effect of carrying the slag bath high the hearth so that itssurface is held in chemically reactive contact with the oxidizing gasesexisting in the combustion zones adjacent to the tuyres is to decreasethe intensity of reduction in the hearth-and to increase retention ofthe manganese in the slag. This measure includes, in the extreme case,carrying the upper surface of the slag bath in contact with, or evenabove, the tuyre level, so as positively to effect bubbling of airthrough the liquid slag. Metallurgically, I am here carrying out, tosome extent, a Bessemerizing process in the neighborhood of the tuyresand pneumatically oxidizing the manganese content of the metal andconcurrently raising the FeO content of the slag above its equilibriumvalue.

6. By increasing the jet velocity of the air blast through the tuyressufficiently, I have found that I can cause (a) lumps of coke to beblown bodily away from the immediate vicinity of the blast entrance and(b) the oxidizing zone to extend farther than usual into the furnace,therer by subjecting an enhanced fraction of the hearth contents tooxidation. A

7. There are two important physical characteristics of a blast furnaceslag which affect the furnace operation, (a) its viscosity and (b) itswetting" property toward coke.

When the slag viscosity is too high, the slag does not flow freelythrough the bosh and into the hearth and this sluggishness of slag flowcauses an accumulation of incombustible material in the combustion zone.As a result, the oxidizing zone contiguous to the tuyres extends tocover an enlarged fraction of the hearth, the intensity of reductionthere is increased, and the FeO in the slag is maintained at the desiredconcentration.

Apart from viscosity considerations, slags con taining substantialamounts of iron and manganese and relatively small amounts of CaO andMsO show an adhesion for coke carbon.

Basic or even slightly acid slags do not wet coke carbon to any materialextent but slags low in lime and magnesia and carrying a considerableamount of manganese silicates have a tendency to adhere to coke carbon.That is to say, they form liquid films which wet" the coke and impairits combustibility. In the present process it is desirable to operatethe furnace with a charge which yields a type of slag which will effecta certain amount of coke wetting.

8. Increasing the water content of the blast above normal moisturecontent, 1. e., operating with a wetted blast, is a powerful means ofimpairing the intensity of hearth reduction. Introduction of water, e.g., as a liquid spray or as live steam, in controlled amount, into theblast, is easily effected in practice, andfunctions in a manner counterto that of a dried blast.

The present invention is defined specifically as a blast furnaceoperation wherein a. substantial departure from equilibrium conditionsis enforced. I have found that it is possible to effect the desireddeparture from equilibrium by employing suitably a variety of operatingfactors, inimicable to thermodynamic equilibrium, such as the eightmeasures above listed.

Each of the several measures above described, either alone or incombination, when used under pro r control, is directed to the one endof results in suppression of manganese metallization and enhancement ofthe FeO content of the slag. Adoption of any one of the eight measuresenumerated above or others of like effect, makes equilibrium value (1.e., a fraction of one per cent at usual blast temperatures), up to, say,one, two, or more, per cent.

The process of the present invention makes possible the maintenance of ahigher FeO value in the slag than thermodynamic equilibrium requires, i.e., the maintenance of non-equilibrium conditions. By thus maintaining ahigh FeO value in the slag I depress the Mn content of the v pig ironand hence effect satisfactory retention of MnO in the slag even whenoperating with such relatively high slag, metal and below 1000 1"., arelatively high ratio of fuel to ore is required in order to keep thefurnace in operation. Although I do not wish to limit the process of thepresent invention to any minimum blast temperature, in the sense that Iam able to make the process operate with cold blast, I have found thatthe economy of the process and the operation of the fumace are greatlyimproved by employment of relatively high blast temperatures. Foreconomical reasons, I prefer to use blast temperatures above 1800 F. Infact, I have found that with blast temperatures in excess of 2000 F., e.g., from 2200' to 2600? F., it is practically impossible to producefurnace difficulties by an indlscretion in the carrying out of theprocess since the slag produced is quite fluid at 2300" F. and thefreezing point of the metal produced is below 2200 F.

No special skill or experience is required for the carrying out of thisprocess. With any given oxidic manganese-iron ore, coke, burden andfurnace, and with high blast temperature available, the furnace can beput into operation according to conventional blast furnace principles.Analysis of Mn in the metal and of FeO in the slag should be taken, andlikewise optical pyrometer readings of the temperatures of the slag atflush and the metal at cast. If the temperature of the slag at flush istoo high (e. g., above 2600 F.), and if Mn in the metal is high (e. g.,4 or 5%), indicating an undesired loss of Mn from the slag, andconjugately if the FeO content of the slag is lower than the limitestablished for the required Mn-to-Fe ratio needed for farm production(e. g., above 3 or 4%), the reducing conditions of the hearth areobviously too intense and one or more of the several special measures,above described, for increasing the FeOcontent of the slag is or arepracticed, and prompt analysis of the FeO content of the slag made ateach flush. As the FeO is increased and the Mn content of the pig irondepressed, the economy of the process can be used as criterionfordetermining the optimum FeO content. The maximum value of FeO in theslag is fixed by the ratio of MnO to FeO in it, in order that the slagshall have the "artificial manganese ore" characteristics abovementioned and be within the "fer-r0 limit (i. e., capable of smelting,in a subsequent operation, to ferromanganese). The ratio of Mn to Fe inthe slag should not be less than 8 to 1, for 80% ferromanganese and, ingeneral, should be 12 or 14 to 1. On the other hand, the minimum limitof FeO in the slag will depend upon the maximum tolerance of manganesein the metal. As a general observation, it may be stated that the Mn inthe metal may desirably be held between 0.5% to 1.0% as a lower limitand 3.5% to 4.0% as an upper limit, and the MnO retained in the slag maydesirably amount at least to 70% of the total manganese content of theore and preferably should amount to from 85% to 95% thereof.

The following specific examples are added to the foregoing descriptionby way of illustration only. The invention is not limited to thespecific conditions enumerated therein, except as may be indicated inthe appended claims.

I may employ a blast furnace of usual design, 86' tall from iron notchto lip ring of the hell, with a charge column measuring 72' verticallyfrom the center line of the tuyeres to the normal stock line: thefurnace has a heath diameter of 14'6", a bosh diameter of 19'0", a bashangle of 76, and a stock line diameter of 12'6". The

active volume of the charge column (between tuyere plane and stockline)- is 14,850 cu. it. Each 20-minute round of 28,000 lbs. of ore and7175 lbs. of coke occupies a volume of 436 cu. ft., and forms a layer onthe stock line 43" thick (average). .The average time of passage of thecharge through the furnace, herein called "time of passage," is 10 hours30 minutes. The stock line descends at an average rate of 2.15 inchesper minute. The furnace is provided with a McKee top," with rotatingdistributor, which device may be adjusted to rotate on a predeterminedschedule. In conventional practice this device is so adjusted as toprovide for uniform distribution of the charge ingredients on the stockvline (i. e., peripheral symmetry of charge).

I charge into this blast furnace, at 20-minute intervals, rounds orcharges consisting of 28,000 lbs. of oxidic u n: -iron ore and 7175 lbs.of coke, and no limestone. Analyses of the ore and coke charged are:

6,350 lbs./t'on 1,568 lbs/ton Ore Joke Fe 33.00 Moisture 1.50 Mn 11.56Volatile P 0.205 matter 1.20 SiOz 8.1 Ash 4.50 A1 0 2.15 Fixed carbon92.80 CaO 0.73 S 0.45 MgO 0.34 Fe 0.78 CO2 0.41 SiOz 2.19 Combined A:1.06 H20 7.89 CaO 0.28 Moisture 14.50 Nitrogen 0.35

I blow this furnace of 16,680 cu. ft. with air preheated to 1900 F. Inthis operation I produce daily 318 long tons of pig iron and 240 longtons of slag. The metal analyzes: Si, 0.25%; S, 0.07; P, .59; Mn, 2.20;C, 3.85; Fe, 93.04. The slag analyzes: S102, 31.40%; A1201, 9.05; CaO,2.96; Mg(), 1.25; FeO, 3.50; no, 51.66; S, 0.31; P205, less than 0.03.The temperature of the emergent metal was 2700* F., and that of the slagwas At the hearth temperature realized in the above illustrativeexample, had there been a reasonable approach to thermodynamic equilib-'rium, the FeO of the slag would have been much lower (less than 1%, forexample) and the manganese in the metal would have been four or five percent.

I was able to produce the above described re sults, which represented amarked departure from equilibrium results, by a variety of means. Forexample, in one mode of carrying out the process of the invention IeiIect non-uniform distribution of the stock on the stock line. I havefound that this maybe done, using a furnace provided with the type oftop above described, by imparting to the charge ingredients a selectedasymmetry or peripheral non-uniformity through appropriate predeterminedadiustment of the schedule of the distributor. Thus, for example, thedistributor may be so rotated as to deposit 17,000 lbs. of the total oreof one round in the first hemicircle and only 1,000 lbs. of ore in thesecond hemicircle. Coke deposition, in accordance with this example. issimilarly affected, 2872 lbs. thereof being deposited in the firsthemicircle and 4303 lbs. thereof being deposited in the secondhemicircle. Thus, the ratio of ore to coke in the first hemicircle ofthe stock line is 5.92 to 1. whereas it is only 2.55 to 1 in the secondhemicircle, although the total ore (28,000 lbs.) and the total coke(7175 lbs.) have the ratio 8.00 to 1.

. By the above distribution I have, in effect, overburdened the firsthemicircle of the furnace and "underburden the second half. If all ofthe iron in that portion of the charge lying in the first half weremetallized, it would mean that only 1025 lbs. of coke had been consumedper ton of pig iron produced. However, this half of the furnace, underthe conditions described, is not able to metallise all of the irontherein because of the under-fueling, and the melted ore rims into thehearth with from 10 to 12% of FeO remaining unreduced. Simultaneously,in the second half of the furnace, where coke is in great excess, ironis metallized with a consumption of 2400 lbs. of coke per ton of metalproduced. This latter, under the conditions described, is a semi-spiegelshowing from 8 to 10% Mn and Si in excess of 1%. The slag flowing intothe hearth on this same side has a very low content of FeO.

As the metals from the respective halves of the furnace flow into thehearth they commingle and diffuse. yielding a metal bath indicating 4 to5% Mn.

In like manner,- the slag (substantially free from M) from second side,commingles with the oxidizing, "high-iron," scouring slag from the firsthalf, and by admixture and diffusion yields a slag containing from 5 to6% FeO.

,Chemical reaction between the FeO of the slag and Mn of the metal takesplace according to Equation 1, and although heat is generated by theexothermic reaction, tending to elevate metal and slag temperatures andthereby to lower the FeO content of the slag, I have found thatopportunity is not aiforded for the two liquids to attain thermodynamicequilibrium and thus that the desired objective is effected. In analternative procedure. while employing conventional symmetricaldistribution at the mum stock line level for any new" or previouslyuntried oxidic manganese-iron ore and thereafter proceed in accordancewith the above principle. It may be remarked here that observance ofthis embodiment of the invention makes possible a material shortening ofthe stack of a furnace to be built for carrying out this process.thereby effecting a saving in the cost of the furnace per se, and alowering of the pressure required to blow the wind into the furnace (i.e., further savings in investment and operating costs intheengineroom).Q

As a third alternative procedure, I maintain conventional symmetricaldistribution on the stock line, maintain the level of the stock line at72' above the tuyeres, but upset the charge column descent by employingan asymmetrical tuyere system. Thus, in the case of an existing blastfurnace provided with 8 symmetrically arranged tuyeres each 4" indiameter, total tuyere cross-sectional area 0,695 sq. ft-., I replacethe tuyeres on the first hemicircle with tuyeres 4%" in diameter and onthe second hemicircle with tuyeres 3%" in diameter. The new tuyeres havethe same total area as the replaced tuyeres, but

two-thirds of the wind is now blown in at the first hemicircle and onlyone-third thereof at the second hemicircle. This causes the rate of cokeconsumption in the first hemicircle to be doubled, and the rate ofdescent of the stock column in that half proceeds twice as fast as inthe other half. Accordingly, the stock line, even' though the charge hadbeen deposited in a uniform manner at the stock line, is caused to dipor become inclined to such an extent that when the average level hasdescended about 10' the plane of the round is inclined about 35 from thehorizontal. The end result of this operation is the same as that flowingfrom asymmetrical distribution (first example above) and as that flowingfrom dropping the stock line (second example above).

stock line, I impair the reduction efficiency of the hearth by droppingthe stock line' a considerable distance below the level conventionallyadhered to. For example, by protraction of the interval of each round to30 minutes (instead of 20 minutes) the level of the top of the stockline is caused to move down in the furnace 0.7" per minute. Bymaintaining this retarded charging schedule for 12 hours, I drop thestock line 42', after which event charging at 20 minute intervals isresumed. With this low stock line (30', as opposed to the former 72'),the average time of passage is decreased from 10 hours 30 minutes toabout 5 hours. This shortening of the charge pecially the combinedwater, the clay content,

and the "caking" or agglomerating characteristics of the ore, thecharacteristics of the fuel,

etc.) no quantitative formula for shortening the time of passage" can belaid down. However, one skilled in the art may, by analyses of the metaland slag, and observation of the slag and metal temperatures, readilydetermine the opti- The inventive objective may, I have found, bereached, with better all-around results, with more opportunity for nicecontrol and with less liability to error due to the "personal equation,"by combining the features (1) a moderate drop in stock line level (15'to 20'), and (2) a limited asymmetry of stock distribution on the stockline (e. g., 5% excess of ore on one side over that on the other side,and 5% excess of coke on the' latter over that on the former), with (3)the employment of tuyeres of 4%" diameter on one side of the furnace andtuyeres of 3%" diameter on the other side. These individually lessdrastic measures combine desirably to bring about injection of suitableamounts of FeO into the hearth with consequent diminution of theintensity of reduction in the latter and the promotion of a slagcontaining by far the greater part of the manganese of the charge'innonmetallized form.

In cooperation with any one or more of the above illustrated measures,(e. g., in cooperation with the combination described immediately above)I may and preferably do employ the measure of oxidizing the slagdirectly with the blast. I control the average upper level of the slagbath, preferably through the agency of a plurality of cinder notches,with associated coolers and monkeys, located at differing distancesbelow the tuyere level, so that the same is in close proximity to theblast entrance. Thus, I may place the topmost cinder notch within 24",or less, of the center line of the tuyeres, and dispose one or,preferably, more cinder notches at spaced intervals therebeneath.

It has been shown that, with run-of-the-oven coke, oxygen gas is foundasfar as 16" to 20" from the blast entrance, and that CO2, in an amountgiving a ratio of CO: to CO as great, as 0.25 to 1 (which amount, athearth temperature, is oxidizing in the reaction Fe-i-COz=FeO+CO) as faras 26" to 30" inwardly from the tuyere nose. Hence, by carrying the slagbath upper surface within 26" to 30" from the tuyere the former isdirectly subjected to gases containing a suiiicient proportion of C: toCO to oxidize some of the iron to R0. when I carry the slag level within16" to 20" from the tuyere the slag encounters gases containing CO: and02, which gases can and do oxidize some of the FeO to F9304, therebyfurther enhancing the oxidizing intensity of the slag.

Considerable decrease in intensity of reduction in the furnace hearthmay be effected by treating some or all of the coke of the charge asfollows: The coke, as formed, is quenched in an aqueous slurry of-clayor other incombustible inert mineral matter, the relative amount of suchmineral matter being adjusted so that the coke when dried carries a thincoating of the mineral matter. I have found that such coatings inhibitprompt combustion of the coke in the latter's arrival in the tuyerezone, and hence diminish reduction intensity.

The use of coke in large lamps serves to extend the dimensions of thecombustion zone and therefore to diminish the intensity of reduction inthe furnace hearth. The linear dimensions of the combustion zone arealmost directly proportional to the linear dimensions of the coke lumps.

An equally effective means of extending the dimensions of the combustionzone is the employment of higher jet velocities of the incoming air. Ihave found that when the jet velocity of the tuyere is increased to anextent such that lumps of coke are blown away from the tuyere nose theintensity of hearth reduction is measurably reduced. Thus, with 2100 cu.ft./min. of air (measured at 60 F. and 30" Hg.) blown through each ofthe eight 4" tuyeres, at 1900 F. hot blast and 14 lbs. gauge pressure inthe hearth, the velocity of the wind, at the tuyere nose, is about 950ft./sec., and its hydrodynamic impact pressure is 3.3 lbs/sq. in. Atthis very considerable pressure the blast forces back the lumps of cokeand tends to produce a so-called "gassy tuyere. Substitution of 3 /2"tuyeres for the 4" tuyeres makes possible raising the jet impactpressure to 5.65 lbs./in., and desirably extends the combustion.Employment of such high jet velocities is limited by consideration ofblowing equipment available, of power consumption, etc.

Perhaps the most convenient and positive of all the methods listed abovefor limiting the free energy of reduction in the hearth, and the onewhich is most easily controlled, is the introduction of added moistureinto the blast. In the above operation I prefer to reduce the burden to26,800 lbs. of ore and 7175 lbs. of coke, per

round, to hold the blast temperature at 1900' F., and to introduce 102lbs. of steam per minute into the hot blast main. This represents about20 boiler horse power, and is an insignificant demand on the boilerroom. I prefer to jet this moisture as boiler steam into the hot blastmain at a point near the stove end, in order to permit diffusion of airand steam before the blast reaches the bustle pipe. The wetted blasthere contains 11% by volume of H20, consumes 3.3% of the carbon beingburned at the tuyeres, and absorbs heat equivalent to one hundreddegrees of hot blast. That is to say. the introduction of 11% of H20vapor into the blast is the thermal equivalent of lowering the blasttemperature F. Its operating advantage lies in the ease and speed withwhich its effect can be controlled.

with the flow of steam into the hot blast main controlled by a valve, Ican sight an optical pyrometer down the tuyere, open the steam valve,and the added moisture arrives at the tuyere nosewithin of a second ofthe time of valve opening; the moisture completes its reaction with hotcarbon in the tuyere zone within /2 second, being converted into C0 andH2, and the complete effect of the steam can be observed withsubstantially no delay.

-A further operating advantage accrues from providing individual steamconnections to the goose necks, or blow pipes,- of the tuyeres, andintroducing 12 lbs. of steam per minute into each tuyere forpredetermined periods of time. Thereby the degree of control possibleover intensity of reduction may be considerably enhanced.

I claim:

1. Process which comprises charging oxidic manganese-iron ore and solidfuel into a blast furnace; blasting the charge with preheated air;maintaining the upper surface of the resulting slag bath at a levelwithin thezone of direct influence of the oxidizing constituents of theblast, whereby the normal reduction intensity of the furnace hearth islessened and a molten slag containing some FeO and at least 70% of thetotal manganese content of the ore in non metallized form and a moltenpig iron product are produced; and tapping off the slag and the moltenpig iron product.

2. Process for the simultaneous production of pig iron and a slagcontaining oxide of manganes and oxide of iron in a ratio of at least 8to 1 from an oxidic manganese-iron ore containing said oxides in alesser ratio, which comprises charging manganese iron ore and solid fuelinto a blast furnace; adjusting the components of the charge to yield astrongly acid slag high in silicates; blasting the charge with preheatedair; and maintaining the upper surface of the resulting slag bath at alevel within the zone of direct influence of the oxidizing constituentsof the blast, whereby the normal reduction intensity of the furnacehearth is lessened and a molten slag containing some Fe() and at least70% of the total manganese content of the are in non-metallized form anda molten pig iron product are produced.

3. Process which comprises charging oxidic manganese-iron ore and solidfuel into a blast furnace in a non-uniform manner such that theproportion of ore to fuel in the several locations in a horizontal planein the shaft of the furnace differs materially from the average ratio ofore to fuel in said horizontal plane, and nonuniform flow of gasesupwardly through the shaft and non-uniform descent of the charge arebrought about, and blasting the charge with preheated air; whereby thenormal reduction intensity of the furnace hearth is lessened and amolten slag containing some FeO and at least 0% of the total manganesecontent of the ore in non-metallized term and a molten pig iron productare produced.

4. In the process of producing molten pig iron and a molten slag byheating oxidic manganeseiron ore with solid fuel, the improvement whichcomprises blasting a charge of the ore and fuel in a blast furnace withpreheated air admitted into the furnace charge as a high velocity jethaving a Jet velocity in excess of 700 feet per second, whereby thenormal reduction intensity of the furnace hearth is lessened and amolten slag containing some FeO and at least 70% of the total manganesecontent of the ore in nonmetallized form and a molten pig ironproductare produced.

5. In the process of producing molten pig iron and a molten slag rich inmanganese compounds by heating oxidic manganese-iron ore with solidfuel, the improvement which comprises establishing and maintaining inthe shaft of a blast furnace a charge column consisting essentially of amixture of the ore and the fuel, blasting the charge with preheated air.and maintaining the charge column so short that raw ore from the chargeis injected into the fluid bath of the furnace hearth.

6. Process which comprises charging oxidie manganese-iron ore and solidfuel into a blast furnace; blasting the charge with preheated air;maintaining the upper surface of the resulting slag bath at a levelwithin the zone of direct influence of the oxidizing constituents of theblast. whereby the normal reduction intensity of the furnace hearth islessened and a molten slag containing more than 1% FeO and a molten pigiron product are produced; and tapp ng 0! the slag and the molten pigiron product.

7. In the process of smelting oxidic manganese-iron ores in the blastfurnace the improvement which comprises blowing a preponderance of thetotal blast through the tuyeres of one side of the furnace, wherebynon-uniform descent oi the charge is effected.

PERCY H. ROYBTER.

